FIG. 2 shows a cross-sectional structural view of a prior art semiconductor laser device. In FIG. 2, reference numeral 1 designates an laser diode (hereinafter referred to as "LD") chip. This LD chip 1 is mounted on a heat sink 2 comprising silver or copper. Spherical lens 3 which is held by copper lens holder 4 which is mounted on heat sink 2 by solder 5 to collimate light from LD chip 1. Heat sink 2 is disposed on iron stem 6.
Silver or copper heat sink 2 is mounted on iron stem 6 so that the light emission point of LD chip 1 coincides with the center axis of stem 6, and copper lens holder so that the axis of lens 3 coincides with the light emission point of LD chip 1. Cap 8' having window glass 7 is welded to this stem 6.
The optical axis alignment in the production process of this prior art laser device will be described.
In this prior art device, the optical axis alignment has been conducted as in the following. That is, a light receiving apparatus is provided opposite to the LD chip 1, and the LD chip 1 is energized to emit light with the lens holder 4 mounted on the heat sink 2 by solder 5. The lens holder 4 is slightly moved in the X and Y direction while monitoring with the light receiving apparatus, and the holder 4 is fixed in a position where the optical axis is aligned. Thereafter, the device is heated and cooked so that the holder 4 is fixed to the heat sink 2 by solder 5.
In the laser device produced as such, the optical axis alignment in the X and Y direction are conducted, and the light emission point of the LD chip 1 is made coincident with the center axis of the stem 6. Accordingly, high coupling efficiency with an optical fiber is obtained.
In the prior art semiconductor laser device, however, there may arise variations in the optical axis alignment positions in the X axis direction due to variations in the attachment positions of the LD chip to the heat sink and variations in the thickness of solder which fixes the lens holder, and accordingly the coupling efficiency with an optical fiber is likely to vary from device to device.